This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Optical mapping technique has been extensively applied to visualize the lethal ventricular fibrillation. The use of this non-invasive, high-resolution method has resulted in many new insights into the initiation and maintenance of ventricular fibrillation.